Neurotransmitters such as histamine, serotonin, dopamine and norepinephrine mediate a large number of processes in the central nervous system (CNS) as well as outside the CNS. Abnormal neurotransmitter levels are associated with a wide variety of diseases and conditions including, but not limited to, Alzheimer's disease, Parkinson's Disease, autism, Guillain-Barré syndrome, mild cognitive impairment, schizophrenia (such as cognitive impairment associated with schizophrenia (CIAS), positive symptoms, disorganized symptoms, and negative symptoms of schizophrenia), anxiety, multiple sclerosis, stroke, traumatic brain injury, spinal cord injury, diabetic neuropathy, fibromyalgia, bipolar disorders, psychosis, depression, attention-deficit disorder (ADD), attention-deficit hyperactivity disorder (ADHD) and a variety of allergic diseases. Compounds that modulate these neurotransmitters may be useful therapeutics.
Histamine receptors belong to the superfamily of G protein-coupled seven transmembrane proteins. G protein-coupled receptors constitute one of the major signal transduction systems in eukaryotic cells. Coding sequences for these receptors, in those regions believed to contribute to the \agonist-antagonist binding site, are strongly conserved across mammalian species. Histamine receptors are found in most peripheral tissue and within the central nervous system. Compounds capable of modulating a histamine receptor may find use in therapy, e.g., histamine antagonists may find use as antihistamines.
Dimebon is a known anti-histamine drug that has also been characterized as a neuroprotective agent useful to treat, inter alia, neurodegenerative diseases. Dimebon has been shown to inhibit the death of brain cells (neurons) in preclinical models of Alzheimer's disease and Huntington's disease, making it a novel potential treatment for these and other neurodegenerative diseases. In addition, dimebon has been shown to improve the mitochondrial function of cells in the setting of cellular stress with very high potency. For example, dimebon treatment improved mitochondrial function and increased the number of surviving cells after treatment with the cell toxin ionomycin in a dose dependent fashion. Dimebon has also been shown to promote neurite outgrowth and neurogenesis, processes important in the formation of new and/or enhanced neuronal cell connections, and evidence of dimebon's potential for use in additional diseases or conditions. See, e.g., U.S. Pat. Nos. 6,187,785 and 7,071,206 and PCT Patent Application Nos. PCT/US2004/041081, PCT/US2007/020483, PCT/US2006/039077, PCT/US2008/077090, PCT/US2007/020516, PCT/US2007/022645, PCT/US2007/002117, PCT/US2008/006667, PCT/US2007/024626, PCT/US2008/009357, PCT/US2007/024623 and PCT/US2008/008121. Hydrogenated pyrido[4,3-b]indoles and uses thereof have been disclosed in PCT Patent Application Nos. PCT/US2008/081390, PCT/US2009/032065 and PCT/US2009/038142. Hydrogenated pyrido[3,4-b]indoles and uses thereof have been described in PCT/US2009/038138. Azepino[4,5-b]indoles and uses thereof have been described in PCT/US2009/062872. All references disclosed herein and throughout, such as publications, patents, patent applications and published patent applications, are incorporated herein by reference in their entireties.
Although dimebon holds great promise as a drug for the treatment of neurodegenerative diseases and/or diseases in which neurite outgrowth and/or neurogenesis may be implicated in therapy, there remains a need for new and alternative therapies for the treatment of such diseases or conditions. In addition, there remains a need for new and alternative antihistamine drugs, preferably ones in which side-effects such as drowsiness are reduced or eliminated. Compounds that exhibit enhanced and/or more desirable properties than dimebon (e.g., superior safety and efficacy) may find particular use in the treatment of at least those indications for which dimebon is believed to be advantageous. Further, compounds that exhibit a different therapeutic profile than dimebon as determined, e.g., by in vitro and/or in vivo assays, may find use in additional diseases and conditions.
Hypertension is a serious condition that can damage vital organs, such as the heart and kidneys, and other parts of the body, such as the central nervous system. Individuals who have hypertension may have, or be at risk of developing, dangerous diseases such as coronary heart disease and kidney failure. Hypertension, which is the leading modifiable risk factor for cardiovascular disease mortality, causes more than 7 million deaths every year worldwide.
Hypertension is the most common chronic medical condition in developed countries as well as the most common indication for physician visits and prescription medication use. Hypertension affects more than 50 million individuals in the United States and over one billion individuals worldwide, and overall prevalence may continue to increase with the advancing age of the population.
Unfortunately, despite the importance of blood pressure control and the availability of multiple classes of antihypertensive agents, the treatment of hypertension remains suboptimal. Data from the most recent National Health and Nutrition Examination Survey demonstrate that only 34% of patients with hypertension have blood pressures at their therapeutic goal. Additionally, it was shown that the majority of patients with hypertension will require two or more antihypertensive agents to achieve their goal blood pressure. Even with optimal compliance with multiple antihypertensive agents of different classes, a significant fraction of patients will not be able to achieve their goal blood pressure. The overall prevalence of resistant hypertension, defined as elevated blood pressure in spite of the use of three or more antihypertensive agents, is unknown, but small studies suggest that it ranges from 5%-16% in primary care settings to greater than 50% in nephrology clinics. Given data suggesting that increasing age and obesity are important risk factors for the development of resistant hypertension, it is expected that the overall prevalence of this condition is likely to increase due to demographic changes in the population.
Systolic blood pressure tends to increase with age and systolic hypertension is an important health issue, prominent in the elderly (Duprez, Am. J. Med. 121:179-184 (2008)). It has been suggested that this occurs as large vessels such as the aorta lose their elasticity with age and is less able to buffer the pulsative nature of cardiac output. There exists a need for a treatment for patients in such clinical setting, for example, patients with systolic hypertension accompanied with low diastolic pressure (Franklin et al. J. Hypertension 29:1101-1108 (2011)).
Metabolic syndrome is a cluster of disorders including obesity, hypertension, hypertrigleridemia, hypercholesterolemia and elevated blood sugar. Individuals with this spectrum of disorders are at increased risk of diabetes, heart disease and stroke. Agents capable of treating more than one of these disorders are desirable.
Hypertensive emergencies are defined as severe elevations in blood pressure associated with resultant organ damage (i.e., pulmonary edema, renal impairment, visual impairment, intracranial hemorrhage, or encephalopathy). The treatment of hypertensive emergencies involves aggressive and controlled blood pressure lowering in a highly monitored intensive care setting using intravenous blood pressure lowering agents. Therapeutic agents and method of treatment is needed to gradually lower blood pressure and minimize damage of end organs such as the brain, kidney, heart, and eye.
The frequency of chronic kidney disease also continues to increase worldwide as does the prevalence of end-stage renal disease. Although chronic kidney disease is often caused by hypertension, other factors such as a decrease in renal blood flow and increase in sodium retention or reabsorption can lead to renal diseases. Increased age and diabetes can also contribute to renal disease. Especially the elderly, which are a growing segment of the world population, are at increased risk for renal disease. The presence of chronic kidney disease is also associated with a large increase in cardiovascular morbidity and mortality. Consequently, the identification and reduction of chronic kidney disease has become a vital public health priority.
Thus, there remains a need for new and useful agents that are capable of (i) reducing an individual's blood pressure and/or (ii) promoting renal blood flow and/or (iii) inhibiting or decreasing sodium reabsorption.
Type 2 diabetes is a serious and prevalent disease. This form of diabetes may involve insulin resistance and impaired insulin release. Approximately 25.8 million people in the United States alone suffer from diabetes, whereby type 2 diabetes accounts for about 90-95% of all diagnosed diabetes cases. From 1980 to 2008 the number of Americans with diabetes has more than tripled. Diabetes is also increasingly prevalent elsewhere, such as in certain Asian countries whose populations have experienced a dramatic increase in the disease. For example, in India and China, where rapid lifestyle and economic changes have led to a more sedentary lifestyle and poorer diet among the overall population, diabetes is becoming a major health concern. In addition, more than a third of adults at least 20 years old have pre-diabetes, which is a significant risk factor for developing type 2 diabetes. Other diseases and indications, such as glucose intolerance and metabolic syndrome may also be associated with impaired insulin release.
There remains a need for new and improved therapies that enhance insulin secretion and/or promote insulin release into the blood stream in individuals who have a reduced or impaired ability to secrete insulin and/or release insulin into the blood stream.